The invention relates to a method of transmitting radio interface information over a bidirectional data link between a base station and a base station controller, said radio interface information comprising signalling information, user information and error control information, and said method comprising inserting the signalling information and user information into ATM cells.
FIG. 1 shows a radio system comprising a fixed part 100 and portable part 130. The fixed part comprises a base station 110 and base station controller 120. The fixed part 100 also comprises a network system and network management system, which are not shown since they are not relevant to the present problem. Between the base station 110 and the portable part 130 there is a bidirectional radio link 140, over which radio interface information is transmitted. The radio interface information comprises signalling information, user information and error control information. The devices of the system use the signalling information to signal with one another and with devices not shown (e.g. the mobile switching centre). The user information is proper payload, e.g. user""s speech or data. The base station 110 preprocesses the information, after which it is transmitted to the base station controller 120.
In the systems of the prior art the signalling information and user information included in the radio interface information are separated from each other in means 116 in the base station 110, whereby the signalling information is transmitted to means 112 and the user information to means 114. Correspondingly, the base station controller 120 comprises means 122 for processing signalling information, means 124 for processing user information and means 126 for recombining the signalling information with the user information. There are separate data links in use between the base station 110 and the base station controller 120: a bidirectional data link 142 for transmitting signalling information and a bidirectional data link 144 for transmitting user information.
The prior art arrangement described above has several disadvantages. If the data links 142, 144 described are not only logically but also physically separate, extra costs will arise from this. It is necessary that both the base station 110 and base station controller 120 have two sets of means 112, 114, 122, 124 for processing separate pieces of information. This increases the production costs of the devices 110, 120 in question. Additional control information has to be transmitted over the data links 142, 144 in order to manage the separate pieces of information, which complicates the processing needed in the base station 110 and base station controller 120. In case the means 112 in the base station 110, which are used for processing the signalling information, have some information on the contents of the signalling information or user information (e.g. if the means 112 have functionality with respect to layer 2 of the OSI. (Open Systems Interconnection) model of the ISO, i.e. the data link layer), it is necessary to change all the base stations 110, if the signalling is altered. This causes considerable maintenance costs for the operator during the use of the system.
The object of the invention is to provide a method of transmitting radio interface information over a bidirectional data link between a base station and a base station controller by means of which the disadvantages of the prior art solutions can be obviated.
This is achieved with the method set forth in the introduction. The method is characterized in that the radio interface information is compressed to fit into at least one ATM (Asynchronous Transfer Mode) cell by replacing the original error control information of the radio interface information with simple status information.
The invention also relates to a system for transmitting radio interface information over a bidirectional data link between a base station and a base station controller, said radio interface information comprising signalling information, user information and error control information, the signalling information and user information being inserted into ATM cells in said system.
The system is characterized in that the base station and base station controller comprise means for compressing the radio interface information to fit into at least one ATM cell by replacing the original error control information of the radio interface information with simple status information.
The method of the invention has several significant advantages. Only one set of means is needed in the base station and base station controller for transmitting the signalling information and user information. According to the invention, the radio interface information is compressed to fit into at least one ATM cell by replacing the original error control information of the radio interface information with simple status information. This is possible since the ATM data link is assumed to be so reliable that it is not necessary to transmit the original error control information of the radio interface information over the ATM data link. The error correction mechanisms of the ATM data link are sufficient. Hence, the structure of the base station and base station controller will be simpler and less expensive, and in addition both the devices will be smaller. The processing needed is much simpler in the base station and base station controller. The signalling information and user information are processed in the base station controller. It is no longer necessary to alter base stations when new signallings are introduced. This allows significant savings on costs for the operator. The invention allows the use of the transmission methods enabled by the ATM, e.g. statistical multiplexing by means of which it is possible to save on costs arising from the construction and/or use of transmission lines. One embodiment of the invention is the DECT-PABX (Digital European Cordless Telephone, Private Automatic Branch Exchange) system, which uses an ATM-based LAN (Local Area Network) as the transmission path.
The advantages of the system of the invention are the same as those described above in connection with the method. Preferred embodiments and other more detailed embodiments of the invention highlight its advantages. It is obvious that preferred embodiments may be combined with detailed embodiments in different ways so as to achieve the desired technical effect.